Phase contrast micrographs of hMSCs during and after selection for SD cells. (Top row) Before recovery of SD cells. (Bottom row) After recovery of SD cells. Passage 2 hMSCs were incubated in complete medium containing 17% FCS for 28 days with a change of medium every 4 days to obtain control cells. Parallel hMSC cultures were incubated under the same conditions in medium without serum to obtain SD cells. The SD cells were then recovered by incubation in medium with 17% FCS for 1 to 5 days. Original magnification, × 10.